Method of forming tubes



July 6, 1926. v

J. H. DUNBAR METHOD OF FORMING TUBES Filed August 27, 1924 4 2 Sheets-Sheet 1 INVENTOR Y 6, 1926.1 r 1 5 6 v J. H. DUNBAR v METHOD OF FORMING TUBES III/4 Patented July 6. 192 6. I

UNITED STATES 1,591,116 PATENT OFFICE.

nuns n. DUNIBAR, or BELLEVERNON, PENNSYLVANIA, AssmNon 'ro PITTSBURGH STEEL PRODUCTS COMPANY, 011' PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

METHOD OF FORMING TUBES.

Application filed August 27, 1824.. Serial No. 734,467.

My invention relates to a method of-making tubes, and particularly to tubes having dividing walls'therein. I

One object. of my invention is to form a tube having a partition or dividing wall therein whose edges tightly fit the interior of the tube at substantially diametrically opposite points, and one end of which partition may terminate short of-the end of the tube so that the tube will be in substance a coil, in that flow may occur therealong in one direction until said end of the wall is reached, whereupon a return flow willbe had alongthe other chamber of the. tube, the tube thus functioning as two connected tubes or as a tube which is provided with a return bend.

Another objectv of my invention is to provide a method whereby an effective seal is procured between the edges of the partition or bglividing plate and the inner wall of the tu Another object of my invention is to simplify and improve generally the structure of and method for making coil units.

Some of the forms which my invention may take, and some of the ways in which it maybe practiced are shown in the accompanying drawings wherein Fig.1 is a'fragmentary view, partially in side elevation and partially in section, showing one manner of practicing my invention; Figs. 2, 3 and 4 are cross sectional views on the lines 2-2, 3-3, and 44 respectively, of Fig. 1; Fig. 5 is a view showing the manner in which a preliminary formation is givento the tube preparatory to performing the operation shown in Fig. 1, Fig. 6 is}; view taken. on the line 6- 6 of Fig. 5; Fi 7 is a view showing the manner in which t o mandrel in Fig. 5 may be removed from the tube; Fig. 8 is a view taken on the line 8-8 of 5; Fig. 9 is a cross sectionalview of a tube formed after the method shown] in Fig. 5; Fig. 10 is a view similar to that of Fig. 1 but showing completion of a tube that has been preformed as in Fig. 5; Fig.

11 is a cross sectional view of the completed tube ofl ig. 10; Fig.12is a sectional view showing one manner, in which tubes formed in accordance with my invention may be used, and Figs. 13 and 14 are cross sectlonal views on the lines 13-13 and 1414, respectively, of Fig. 12.-

Referring now more particularly to Fig. 1, I have shown a fragmentary portion of a mandrel 15 which may be of somewhat the usual form but is provided with a slot 16 extending longitudinally thereof, from its forward end to a point adjacent to the rear end thereof. The mandrel 15 is provided at its forward end with a plug 17 that is also slotted, and is supported from a frame 18, being held against forward movement by a nut 19 that has screw-threadedengagement After the plate 20- and the tube 22 have been placed in position upon the mandrel 15, the die block 21 is moved into alignment therewith and the forward end 23 of the tube is grasped by tongs or in any other manner to draw the'tubev forward as indicated by the arrow. The opening through the die block 21 is of such size that-the tube is reduced in diameter. as it passes therethrough, thus causing it to tightly engage the edges of the plate 20.

I Fig. 4 is a cross sectional view showing the arrangement andspacing of the tube 22, the plate 20 and the mandrel 15 previous to the drawing operation. Fi'. 3 is a similar view showing the relation 0 the parts when the drawing: operation 'is. partlally completed, and ig. 2 is a cross sectional view .of the completed article.

After completion of the drawing operation just. described, the end-of the tube may be cut off and capped, the partition plate 20 being of shorter length than the tube so that fluid flowing through the chamber or pa s sage formed at one .side of the wall, may

pass the end of the diyiding' plate and have a return flow through he passage at the opposite sideof the plate. In Figs. 5 to 11, I show a modified form of completed tube and a method for forming the same. The tube 22' of Fig. 5, before vi e having the dividing wall inserted therein, is first drawn over a mandrel 24 that has ribs 25 (Fig-. 8) so that longitudinal grooves will be formed in the tube. The mandrel 24 ex-.

tends through a die block 26 and moves the tube is enlarged slightly as shown in Fig.

7, to permit withdrawal of the mandrel 24.

The tube 22 is then ready for an operation similar to that described in connection with Fig. 1, its cross sectional form being indicated in Fig. 9. The'mandrel 15 may be supported in a manner similar to the mandrel 15 and a partition plate 16 inserted therein, the tube 22 being so positioned that its longitudinal grooves will lie opposite to or be partiall engaged by the edges of the slate-16. T e drawing operation through ie blocks 21 is then performed, to shrink -or reducethe tube to a size that will cause the edges of the plate '16 to be seated snugly within the grooves of the tube as shown in 11. The grooves not only serve to proa tight joint as between the edges of the plate 16 and the tube, but may serve as ameans for holding the plate and the tube in proper diametrical relation during the drawing operation. This latter function,

however, may be satisfactorily performed bythe slot 16 in the mandrel 15 or sand or wax cores inserted between the sides of' the plate and the inner wall of the tube.

In Fig. 12 I have shown one manner in which tubes as above described may be employed. The tube 22 in this case, is represented as a superheater tube disposed within plate. I

The method which consists in forming longitudinal grooves upon the inner walla smoke tube 28 that extends from the usual ifire box sheet 29 to a front tube sheet 30.;

The chambers or passages of the tube 22* at their forward ends have communications nective opening31 of one tube to opening 32 of. an adjacent tube, and so on, a coil-like system would be secured requiring but onehalf the number of tubes usually required for a given length of travel.

Various changes in detail of construction and method of operation may be made with-- out departing from the spirit and scope of the invention as defined in the accompanying claims. v

I claim as myinvention:

1. The method which consists in supporting a partition plate throughout substantially its entire length, placing atube over said plate and its support, and'drawing said tube and plate through a reducing die, to compress said tube against the edges of the of a tube, inserting a partition plate in said tube with its edges seating in said grooves.

and reducing the diameter of said tube by drawing it longitudinally through a reducing die.

3. The method which consists in forming longitudinal grooves upon the inner wall of a tube, inserting a partition plate in said tube with -its edges disposed adjacent to and in parallelism with said grooves, and reducing the diameter of said tube by drawing it longitudinally through a reducing die.

In'testimony whereof I the said J Arms H. DUNBAR, have hereunto set my hand.

JAMES DUNBAR. 

